The present invention relates to calenders in general, and more particularly to improvements in calenders of the type wherein at least one of the rolls has a hollow cylindrical member which spacedly surrounds a shaft-like carrier and confines a displacing device serving to counteract the tendency of the cylindrical member to undergo deformation when the calender is in use.
German Auslegeschrift No. 22 54 392 discloses a calender wherein the lowermost roll of the roll train has a hollow cylindrical member surrounding a row of spaced-apart hydrostatic cylinder and piston units which compensate for deformation of the cylindrical member in response to stresses that develop when the calender is in use. More specifically, the just mentioned units serve to prevent undue deformation of the cylindrical member and to thus ensure that the peripheral surface of the cylindrical member is in proper linear contact with the peripheral surface of the adjacent roll. The carrier for the cylindrical member does not rotate and its end portions are mounted in bearings which are movable up and down relative to the stand. The end portions of the adjacent (next-to-the-lowermost) roll are also mounted in bearings which are movable up and down along suitable guide means on the stand. The pressure of fluid in the chambers of the aforementioned cylinder and piston units must suffice to compensate for the weight of the cylindrical member, for the weight of the remaining rolls of the roll train, for the stresses which develop as a result of reaction of the treated material while such material is conveyed through the calender, as well as to counteract the tendency of the cylindrical member to undergo deformation when the calender is in use. Each change in stressing of the cylindrical member entails a change in the flexing or bending forces and vice versa. This means that the regulating unit which controls the pressure in the cylinder chambers of the various cylinder and piston units must react to a host of variable parameters. The cylindrical member is most likely to be deformed in the region midway between its ends because the adjacent roll or counterroll is mounted in bearings which engage its end portions so that the median portion of such counterroll tends to bend and to apply a deforming stress to the cylindrical member of the lowermost roll.